The present invention relates to a photographic roll film such as Brownie film, particularly a sealing tape, used for the photographic roll film, which can seal a roll of film easily and reliably with no need to lick adhesive on a sealing tape as in a conventional one.
A photographic roll film such as Brownie film is made of an approximately 6 cm wide photographic film strip which is wound around a spool and secured by a sealing tape. 120 type and 220 type are well known as the roll film products. A film strip of the 120 type is covered with a light-shielding backing paper (so-called xe2x80x9cleader paperxe2x80x9d) which is longer than the film strip. A film strip of the 220 type has a light-shielding leader paper (so-called xe2x80x9cleaderxe2x80x9d) spliced to a leading end portion thereof and a light-shielding trailer paper (so-calledxe2x80x9ctrailerxe2x80x9d) spliced to a trailing end portion thereof, which is about twice as long as the 120 type.
The film strip of the roll film wound around a spool loaded in a loading chamber of camera is wound by a take-up spool set in a winding chamber of the camera as an exposure is made. A trailing end of the film strip and a trailing end of the light-shielding backing paper or the light-shielding trailer are detached from the spool in the loading chamber to be wound up around the take-up spool in the winding chamber. A sealing tape, of which part is coated with an adhesive to be activated by being wet, is secured to the outer surface of the trailing end portion of the light-shielding paper.
A user detaches the roll of film wound around the take-up spool from the camera, then partially pulls up the sealing tape to lick and activate the adhesive coated portion and pastes the portion on the surface of the light-shielding paper across the trailing end edge to seal the roll of exposed film while keeping the light-shielding paper tight by using his fingers. It is, however, unpleasant and unsanitary to lick the adhesive and may be bad for the health of a heavy user. Sealing tapes which work without getting wet have been developed.
Japanese Laid-open Patent 104803/98 (tokkai-hei 10-104803) shows a roll film of which sealing tape secured to a light-shielding paper on its trailing end portion has an adhesive/tacky layer portion and a release layer portion on the same side which directly face each other by folding the tape over. After exposing the entire photographic film strip, the sealing tape is unfolded and the adhesive layer portion is adhered to a light-shielding paper to seal.
Japanese Laid-open Patent 271935/99 (tokkai-hei 11-271935) shows a roll film of which sealing tape is folded in a Z-shape to make an adhesive layer portion and a release layer portion that directly face each other.
Japanese Laid-open Patent 271936/99 (tokkai-hei 11-271936) shows a sealing tape coated with an adhesive which is divided into three portions by placing a release layer on a light-shielding paper, a secured-to-light-shielding-paper portion, an easily peelable portion facing the release layer and a provisionally-secured-to-light-shielding-paper portion which is peeled off after exposing the entire photographic film strip. Most of the sealing tape other than the secured-to-light-shielding-paper portion can be used as an adhesive tape for sealing the roll of film.
In the roll film shown in the above-noted Japanese Laid-open Patent 104803/98 (tokkai-hei 10-104803), however, the adhesive material tends to cause contamination and broken portions of the sealing tape may be left in the camera. As shown in FIG. 25, the sealing tape 82 is secured to the light-shielding paper only on its trailing end portion, which causes the sealing tape to be bent when the light-shielding paper is transported in the camera and a leading edge of the sealing tape 82 hits an end of spring member 81 for preventing the roll of film from loosening. In the following stage as shown in FIG. 26, the sealing tape 82 is bent over along a line close to the trailing end portion, which causes a border area between the adhesive layer and the release layer to be exposed, and then the bent sealing tape is transported as shown in FIG. 27. Finally, as shown in FIG. 28, the originally folded-over portion including the tacky layer and the release layer inside becomes unfolded to expose respective layers by a film supporting member 83 of the camera, which may cause contamination with the tacky material or leave a broken portion of the sealing tape in the camera.
In the sealing tape folded in a Z-shape as disclosed in the above-noted Japanese Laid-open Patent 271935/99 (tokkai-hei 11-271935), edges of a pair of a tacky layer and a release layer are exposed, which causes the same problem such that the folded-over portion including the pair of layers becomes unfolded as the sealing tape on the light-shielding paper advances in the camera and causes tacky contamination.
In the sealing tape in the above-noted Japanese Laid-open Patent 271936/99 (tokkai-hei 11-271936), it is inconvenient and not so easy to peel off the leading edge of the sealing tape which is provisionally secured to the light-shielding paper.
An object of the invention is to provide a photographic roll film which can be sealed easily and reliably with no need to lick adhesive on a sealing tape as in a conventional one.
To accomplish the object, the following photographic roll film with improved sealing tape is provided.
A photographic roll film comprising: a spool, a roll of photographic film strip wound around the spool, a light-shielding paper for covering the roll of the photographic film strip, and a sealing tape for keeping the light-shielding paper covering the roll of the photographic film strip without loosening wherein the sealing tape includes a bonding portion and a release portion which are made of single tape base. A first bond layer is coated on the tape base in the bonding portion for securing a first end of the sealing tape to a surface of the light-shielding paper and a folded-over portion is formed in the release portion by folding over the tape base. A first tacky layer and a release layer are separately coated on the tape base inside the folded-over portion and directly face each other, and a second end of the tape base is secured to an end portion of the first bond layer. The photographic roll film may be provided with a second bond layer or a second tacky layer that is coated on the second end portion of the tape base and glued to the first bond layer.
The invention further provides a tab for easily unfolding the sealing tape, which is formed in the tape base of the folded-over portion accompanied by a perforated-line for tearing off a part of the tape base to unfold the folded-over portion and expose the first tacky layer by which the light-shielding paper around the roll of photographic film strip is sealed.
Usually the tab and the first tacky layer are located close to each other to make the effective sealing length as long as possible. Thus, the tab and the first tacky layer are formed on the same part of the tape base with respect to the folded-over portion.
Usually the sealing tape is secured to the outer surface of the light-shielding paper. In the present invention, it is possible to fix the sealing tape on the inner surface of the light-shielding paper.
For this purpose, the invention provides for the bonding portion to be secured to an inner surface of the light-shielding paper so as to be located in the leading side of the sealing tape in the film advancing direction, and the tab and the first tacky layer are formed with respect to one side tape base of the folded-over portion away from the light-shielding paper. In this case, the tab is located outside of the sealing tape, which makes it easier to pick up the tab.
Some other modified sealing tapes are also developed as discussed below, where the release portions are formed to have an S-shape or a Z-shape.
As S-shaped, the sealing tape includes a bonding portion and a release portion which are made of a single tape base, the bonding portion has a first folded-over portion formed by folding over the tape base and a first bond layer coated in one side of the first folded-over portion for securing a first end of the sealing tape to a surface of the light-shielding paper. The release portion is made of a second folded-over portion and is formed by folding over the tape base, which is connected to the first folded-over portion to form the S-shape, and includes a first tacky layer and a release layer that are separately coated on the tape base inside the second folded-over portion and directly face each other. A tab is formed in the second folded-over portion accompanied by a perforated-line for tearing off a part of the tape base to unfold the second folded-over portion and expose the first tacky layer to seal the light-shielding paper. A second bond layer or a second tacky layer is coated on the second end portion of the tape base and is secured to the tape base.
The invention provides for another S shape wherein the sealing tape includes a bonding portion and a release portion which are made of a single tape base. The bonding portion has a first folded-over portion formed by folding over the tape base and a bond layer for securing the sealing tape to a surface of the light-shielding paper. The release portion is made of an S-shaped folded-over portion formed by folding the tape base twice and includes a tacky layer and a release layer inside the upper fold-over of the S-shaped folded-over portion which are coated on the tape base separately and directly face each other and an adhesive layer inside the lower folded-over of which adhesive strength is less than that of the bond layer of the bonding portion so that a user can easily peel it off.
As Z-shaped, the sealing tape includes a bonding portion and a release portion which are made of a single tape base, the bonding portion has a bond layer coated on the tape base for securing the sealing tape to a surface of the light-shielding paper. The release portion, made of a folded-over portion formed by folding over the tape base, includes a tacky layer and a release layer that are separately coated on the tape base inside the folded-over portion and directly face each other, and a second end portion of the tape base is folded back to form the Z-shape. This fold back portion can be an alternative for the tab.
As a further modified S-shape, the sealing tape includes a bonding portion and a release portion which are made of a single tape base, the bonding portion has a first folded-over portion formed by folding over the tape base and a bond layer coated on one side of the first folded-over portion for securing the sealing tape to a surface of the light-shielding paper. The release portion is made of a second folded-over portion formed by folding over the tape base, which is connected to the first folded-over portion to form the S-shape, and includes a tacky layer and a release layer inside the second folded-over portion which are coated on the tape base separately and directly face each other, and a second end portion of the tape base is folded back.